Folks who spend the health insurance open season watching football on television, Christmas shopping or doing anything to avoid their health insurance homework could be making a costly mistake.

Call it coverage by default.

Sleepwalking through the open enrollment period--which runs through Dec. 13--means one of two things could happen to you:

1) If your current health plan remains in the federal health program next year, you will be reenrolled in it automatically. If you do nothing.

2) If your 1999 health plan is leaving the federal health program at the end of the year, you will be enrolled automatically in the Blue Cross-Blue Shield standard option plan next year. If you do nothing.

Over the years, many fee-for-service plans have dropped out, including plans sponsored by the American Federation of Government Employees, the National Association of Government Employees, the National Treasury Employees Union and the National Federation of Federal Employees. Generally, they had too few people, too many sick people or both, and they lost money.

The once-top-rated BACE plan (Beneficial Association of Congressional Employees) also has dropped out. When BACE was launched, its benefits were great, and its premiums were low. It was the choice of Vice President Gore, who as president of the Senate and a former senator was eligible for family coverage. But BACE lost members and was hit by heavy medical bills.

People in plans that dropped out of the federal program--and who didn't pick a replacement--were all put into the Blue Cross standard plan. It's the biggest plan in the federal health program. It's also an excellent plan, with low premiums, but you probably don't want to enter any plan by default.

Most of the dropout health plans have been health maintenance organizations, which provide coverage in particular local areas.

Over the past two years, about 100 HMOs have left the federal program or were absorbed by other HMOs. In some parts of the country, federal workers don't have any HMOs to choose from.

HMOs available to federal workers and retirees in the Washington area next year are: Kaiser Permanente, George Washington, Aetna US Healthcare, Prudential, M.D. IPA, CapitalCare and Free State. Aetna is the only HMO in the Washington area that will offer both standard- and high-option plans next year.

If your current HMO is being absorbed by another, you will be put into the other HMO next year. If you do nothing.

Fee-for-service plans (which are nationwide) available next year are Blue Cross, Postmasters, Mail Handlers, GEHA, American Postal Workers Union, National Association of Letter Carriers and Alliance. Those are open to all federal workers and retirees. In addition, there are special plans restricted to groups of workers in specific agencies. They are Association Benefit, SAMBA, Foreign Service, Secret Service and Rural Letter Carriers.

People who do nothing during the open season won't lose coverage. But some could find themselves in a strange, new (to them) plan next year, or they could wind up with reduced benefits or higher premiums in their current plan.

Once you find a plan that looks good, ask your doctor or dentist to look over the brochures to see whether the plan works for both of you. If your doctor is part of the plan's preferred-provider option, you can save a lot of money next year.

Besides your health plan brochure and your doctor, here are other good sources of health plan information:

* The Washington Consumers' Checkbook Guide to Health Plans for Federal Employees is available at most area drugstores and bookstores. The guide rates plans by benefits and number of complaints, and it lists premiums and likely total out-of-pocket costs for each plan. The guide costs $8.95. It is available (for $10.95) by mail from Checkbook--Health Insurance, 733 15th St. NW, Suite 820, Washington, D.C., 20005 or by calling 202-347-7283.

* The December issue of Retirement Life, the magazine of the National Association of Retired Federal Employees, will have a special health benefits section for active-duty workers and retirees. NARFE members will get the magazine automatically. NARFE says anyone signing up by Nov. 18 also will receive the magazine and health benefits insert. NARFE can be reached by writing to 606 N. Washington St., Alexandria, Va. 22314-1914, or by calling 1-800-627-3394.

* The Washington Post (including this column), Federal Times and other publications will continue to run articles on health insurance during the open season.

Mike Causey's e-mail address is causeym@washpost.com.